The present invention relates to a semiconductor device, a manufacturing method thereof, a lead frame, a manufacturing method thereof, and a manufacturing method of a semiconductor device using a lead frame, and more particularly, to a leadless surface-mount resin-sealing semiconductor device, a manufacturing method thereof, a lead frame, a manufacturing method thereof, and a manufacturing method of a semiconductor device using a lead frame.
Recently, as electronic apparatuses become smaller and highly functional, semiconductor devices provided in these electronic apparatuses also become smaller and thinner at a rapid pace. When semiconductor devices become smaller and thinner, it becomes difficult to efficiently dissipate heat generated in a semiconductor element.
Thus, a new structure to efficiently dissipate heat generated in a semiconductor element is desired even for semiconductor devices made smaller and thinner.
FIG. 1 and FIG. 2 show conventional semiconductor devices 10A and 10B.
Each of the semiconductor devices 10A and 10B shown in the respective figures has a considerably simple structure comprising a semiconductor element 11, a wire 12, a terminal 15, a resin package 16 and so forth. A resin projection 18 protruding downward from a mount surface 16a of the resin package 16 is formed unitarily with each of the semiconductor devices 10A and 10B The resin projection 18 is coated with a metal film 19 so as to form the terminal 15.
Additionally, in the semiconductor device 10B shown in FIG. 2, a backside terminal 17 is formed on the mount surface 16a of the resin package 16. This backside terminal 17 is a conductive metal film as is the metal film 19, and is so structured as to be electrically connected to a ground terminal on a mounting substrate (not shown in the figures) upon mounting the semiconductor device 10B on the mounting substrate. Accordingly, in the mounting state, the backside terminal 17 functions as a shield member shielding the semiconductor element 11 so as to improve electric characteristics of the semiconductor device 10B.
Since the semiconductor devices 10A and 10B structured as above are not provided with an inner lead and an outer lead as in an SSOP, an area for drawing around from the inner lead to the outer lead and an area of the outer lead per se become unnecessary so as to miniaturize the semiconductor devices 10A and 10B.
Additionally, a loading substrate (an interposer) for forming a solder ball, such as a BGA (Ball Grid Array), also becomes unnecessary so as to reduce costs of the semiconductor devices 10A and 10B. Further, the terminal 15 composed of the resin projection 18 and the metal film 19 exhibits a function equivalent to a solder ball in co-operation so as to obtain a mounting property similar to a semiconductor device of a BGA type.
By the way, as the semiconductor element 11 becomes highly dense recently, an amount of heat generated in the semiconductor element 11 tends to increase. However, since a coefficient of thermal conductivity of resin is low in a resin-sealing semiconductor device, a heat-dissipation characteristic becomes inferior.
Additionally, since the terminal 15 is structured by coating the resin projection 18 with the metal film 19 in the semiconductor devices 10A and 10B shown in FIG. 1 and FIG. 2, an amount of heat dissipation from a mounting terminal is as small as a BGA having a solder ball as a mounting terminal and a QFP (Quad Flat Package) having a lead as a mounting terminal. Therefore, although the semiconductor devices 10A and 10B shown in FIG. 1 and FIG. 2 have the above-mentioned favorable characteristics, the semiconductor devices 10A and 10B have insufficient heat-dissipation characteristics so as to incur a problem that a malfunction is caused in the semiconductor element 11 by the generated heat.
It is a general object of the present invention to provide an improved and useful semiconductor device, a manufacturing method thereof, a lead frame, a manufacturing method thereof, and a manufacturing method of a semiconductor device using a lead frame in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device capable of efficiently dissipating heat generated in a semiconductor element, a manufacturing method thereof, a lead frame, a manufacturing method thereof, and a manufacturing method of a semiconductor device using a lead frame.
In order to achieve this object, the present invention, which is a semiconductor device comprising a semiconductor element, a resin package sealing the foregoing semiconductor element, a plurality of resin projections formed on a mount side of the foregoing resin package so as to protrude thereon, a metal film provided on the foregoing resin projection, and a wire electrically connecting an electrode pad on the foregoing semiconductor element and the foregoing metal film to each other, is characterized in that a heat-dissipation member is provided opposite the foregoing semiconductor element so as to dissipate heat generated from the foregoing semiconductor element, and a projection amount of the foregoing heat-dissipation member from the foregoing mount surface is arranged to be equal to or smaller than a projection amount of the foregoing resin projection including the foregoing metal film.
According to the present invention, the heat-dissipation member dissipating heat generated from the semiconductor element is provided opposite the semiconductor element such that the heat generated in the semiconductor element is dissipated at the heat-dissipation member. Therefore, the semiconductor element can be cooled efficiently so as to prevent a malfunction from occurring in the semiconductor element.
Additionally, since the projection amount of the heat-dissipation member from the mount surface is arranged to be equal to or smaller than the projection amount of the resin projection including the metal film, the heat-dissipation member does not thwart a joining of the metal film and a mounting substrate upon mounting the semiconductor device.
Additionally, in the above-mentioned semiconductor device, the present invention is characterized in that the foregoing heat-dissipation member is a metal plate formed of a lead-frame material.
According to the present invention, the heat-dissipation member is provided as the metal plate formed of the lead-frame material so as to obtain an excellent heat-dissipation characteristic because the lead-frame material has a high coefficient of thermal conductivity.
Additionally, in the above-mentioned semiconductor device, the present invention is characterized in that at least one metal layer is provided between the foregoing semiconductor element and the foregoing heat-dissipation member, and the foregoing heat-dissipation member is fixed to the foregoing metal layer by bonding.
According to the present invention, at least one metal layer is provided between the semiconductor element and the heat-dissipation member, and the heat-dissipation member is fixed to the metal layer by bonding so that a material having an excellent adhesiveness can be used as the metal layer so as to fix the heat-dissipation member firmly. In addition, since the metal layer per se has a thermal conductivity, the heat generated in the semiconductor element can be efficiently transferred by thermal conduction to the heat-dissipation member.
Additionally, in order to achieve the above-mentioned object, the present invention, which is a semiconductor device comprising a semiconductor element, a resin package sealing this semiconductor element, a plurality of resin projections formed in a peripheral form on a mount side of this resin package so as to protrude thereon, a metal film provided on this resin projection, a backside terminal formed inside positions on the foregoing mount side at which the foregoing resin projections are provided so as to protrude thereat, a wire electrically connecting an electrode pad on the foregoing semiconductor element and the foregoing metal film to each other, is characterized in that a heat-dissipation member is provided between the foregoing semiconductor element and the foregoing backside terminal.
According to the present invention, the heat-dissipation member is provided between the semiconductor element and the backside terminal so that the heat generated in the semiconductor element is first transferred by thermal conduction to the heat-dissipation member, and thereafter is transferred by thermal conduction to the backside terminal so as to be emitted to outside. In this course, since the backside terminal is joined to the mounting substrate on which the semiconductor element is mounted, the heat generated in the semiconductor element is transferred by thermal conduction to the mounting substrate, and is dissipated also at this mounting substrate. Thus, providing the heat-dissipation member between the semiconductor element and the backside terminal enables an increase in a heat-dissipation capacity so as to perform an efficient heat-dissipation process.
Additionally, in the above-mentioned semiconductor device, the present invention is characterized in that the foregoing semiconductor element is placed on the foregoing heat-dissipation member.
According to the present invention, the semiconductor element is placed directly on top of the heat-dissipation member so that the heat generated in the semiconductor element can be directly dissipated to the heat-dissipation member so as to improve a heat-dissipation efficiency. Also, the heat-dissipation member can be used as a substrate on which the semiconductor element is mounted.
Additionally, in order to achieve the above-mentioned object, the present invention, which is a manufacturing method of the above-mentioned semiconductor device, is characterized by comprising a lead frame forming step of forming a lead frame by preparing a substrate formed of the lead-frame material, forming a receding portion at a position in the foregoing substrate corresponding to a position at which the foregoing resin projection is formed, and coating inside of the foregoing receding portion with the foregoing metal film, an element mounting step of mounting the foregoing semiconductor element on the foregoing lead frame, and electrically connecting the foregoing semiconductor element ad the foregoing metal film to each other by the foregoing wire, a sealing step of forming the foregoing resin package sealing at least the foregoing semiconductor element and the foregoing wire, a first lead frame removing step of removing the foregoing lead frame so that a thickness of the foregoing lead frame becomes equal to or smaller than a height of the foregoing resin projection including the foregoing metal film from the foregoing mount surface, and a second lead frame removing step of providing a resist material at a predetermined position on the foregoing lead frame at which to form the foregoing heat-dissipation member, and thereafter, removing the foregoing lead frame on which the foregoing resist is not provided so as to form the foregoing heat-dissipation member.
In the present invention, the lead frame formed in the lead frame forming step is removed after the element mounting step and the sealing step are finished. In this course, firstly, the first lead frame removing step is performed so as to perform a removing process of the lead frame such that the thickness of the lead frame becomes equal to or smaller than the height of the resin projection including the metal film from the mount surface. At the point of completion of this removing process, the metal film shares substantially the same plane as the lead frame, or protrudes slightly from the lead frame.
Next, the second lead frame removing step is performed so as to provide the resist material at the predetermined position on the lead frame at which to form the heat-dissipation member, and thereafter, remove the lead frame on which this resist is not provided. Thereby, the position on the lead frame at which the resist material is provided remains on the mount surface so that this portion becomes the heat-dissipation member.
Thus, utilizing the lead frame used upon manufacturing the semiconductor device, a part of the lead frame is caused to remain, in the first and second lead frame removing steps, so that the part becomes the heat-dissipation member; therefore, manufacturing steps can be simplified, compared to a method of forming a heat-dissipation member from a material different from the lead frame. In addition, a new manufacturing facility for forming the heat-dissipation member is also unnecessary so that facility costs do not increase.
Additionally, in order to achieve the above-mentioned object, the present invention, which is a lead frame used upon manufacturing a semiconductor device comprising a semiconductor device, a resin package sealing the foregoing semiconductor device, a resin projection formed on a mount surface of the foregoing resin package so as to protrude thereon, a metal film provided on the foregoing resin projection, and connecting means for electrically connecting an electrode pad on the foregoing semiconductor element and the foregoing metal film to each other, is characterized in that a receding portion formed at a position in a base corresponding to a position at which the foregoing resin projection is formed, the receding portion having the foregoing metal film formed therein, is formed at both surfaces of the foregoing base.
Additionally, in the above-mentioned lead frame, the present invention is characterized in that the foregoing metal film is a four-layer structured film of a solder layer, a nickel (Ni) layer, a palladium (Pd) layer, and a gold (Au) layer, from an inner layer, or a four-layer structured film of a palladium (Pd) layer, a nickel (Ni) layer, a palladium (Pd) layer, and a gold (Au) layer, from the inner layer.
Additionally, in the above-mentioned lead frame, the present invention is characterized in that the foregoing base is composed of first and second half bases at one surface of each of which the foregoing receding portion is formed, and surfaces of the foregoing first and second half bases at which the foregoing receding portion is not formed are joined to each other.
Additionally, in order to achieve the above-mentioned object, the present invention, which is a manufacturing method of the above-mentioned lead frame, is characterized by comprising a resist applying step of applying etching resists on both surfaces of the base, a resist pattern forming step of forming predetermined resist patterns by removing portions of the foregoing etching resists corresponding to the foregoing receding-portion forming positions, an etching step of forming the receding portions at the foregoing receding-portion forming positions at both surfaces of the foregoing base by using the resist patterns as masks, a metal-film forming step of forming the foregoing metal films in the receding portions formed in the foregoing etching step, and a resist removing step of removing the foregoing etching resists.
Further, in order to achieve the above-mentioned object, the present invention, which is a manufacturing method of a semiconductor device by using the above-mentioned lead frame, is characterized by comprising an element mounting step of mounting the semiconductor element on the foregoing lead frame, a connecting step of electrically connecting an electrode pad formed on the foregoing semiconductor element and the foregoing metal film formed in the foregoing lead frame to each other, a sealing step of forming a resin on the foregoing lead frame, the resin sealing the foregoing semiconductor device, so as to form the resin package, a dividing step of dividing the foregoing lead frame into the foregoing first half base and the foregoing second half base, and a separating step of separating the foregoing resin package together with the foregoing metal film from the foregoing first and second half bases.
According to the lead frame, the manufacturing method of the lead frame, and the manufacturing method of a semiconductor device by using the lead frame, of each of the above-mentioned inventions, a lead-frame cost required for manufacturing one semiconductor device can be reduced, and thus a manufacturing cost can be reduced. In addition, since a multitude of the semiconductor devices can be formed all at one time, a manufacturing efficiency can be improved.